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Figure 12. Change in Z-average size after addition of sodium dithionite over 130 minutes
The data from the sodium dithionite experiment shows promising results for the Pluronic® F68 and Pluronic® F127 particles, but show poor results for the Pluronic® P85 particles. The desired result for this experiment was for the particles to increase in size from time zero to 130 minutes. An increase in size would mean that sodium dithionite effectively reduced the polyQPA portion of the particles and thus carried out the
proposed mechanism from Figure 4. The resulting reduced particle would have a result as shown in Figure 7. As a result, the individual units of the polyQPA-Pluronic® particles dissociate from one another and an overall increase in size is the result, as shown in Figure 7.
0 500 1000 1500 2000 2500
0 20 40 60 80 100 120 140
Z-average size (nm)
Minutes
Change in Z-average size after addition of sodium
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For Pluronic® F68, the general trend is an increase in size until 110 minutes, after which time the size begins to decrease slightly. The overall general increase however does show that the polyQPA-Pluronic® F68 structure should be effective for future incorporation and release of paclitaxel. For Pluronic® F127, the trend also was increase but ended at 90 minutes, after which the size also decreased slightly. Nevertheless, these results show promise as well for future incorporation and release of paclitaxel.
However, Pluronic® P85 showed very erratic results for changes in size over 130 minutes. Therefore, the polyQPA-Pluronic® P85 structure most likely does not support the mechanism in Figure 4 and is not a good system for future incorporation and release of paclitaxel. Another reason for the ineffectiveness of the polyQPA-Pluronic® P85 structure is that there was a mistake made in synthesis and the copolymeric nanoparticles were not correctly made. This mistake would account for the problems in size and
stability and in sodium dithionite reduction.
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CONCLUSION
According to the results of the experiments, polyQPA-Pluronic® block copolymeric nanoparticles are viable possibilities for future drug delivery. Both
polyQPA-Pluronic® F68 and F127 showed successful and promising results for size and stability measurements as a well as sodium dithionite reduction. However, polyQPA- Pluronic® P85 showed erratic results for both experiments.
Conclusions can be drawn from the results of this experiment and thus can be integrated into future research for redox-sensitive chemotherapy drug delivery systems.
First, Pluronic® was well incorporated with polyQPA. This conclusion can be drawn because of the size difference between polyQPA-mPEG750 and polyQPA-Pluronic®. The mean diameter of micelles of poly-mPEG750 in preliminary research was 27.50 nm whereas the diameters of the various polyQPA-Pluronic® nanoparticles were at least 400 nm (Bae and Maurya et al. 5). Therefore, the Pluronic® changed the size of the particles, and it also affected to the stability of the particles over time. Furthermore, it is known that polyQPA can still perform its function of releasing QPA lactone is because the sodium dithionite experiment was successful for polyQPA-Pluronic® F68 and F127.
The second conclusion that can be drawn from this experiment is that Pluronic® with long PEO chains are more effective for stability like with Pluronic® F68 and F127.
This phenomenon is due to the fact that having more hydrophilic nature from PEO prevents the hydrophobic portions of the molecules in polyQPA and hydrophobic PPO portion of Pluronic® from self-aggregating and having low solvency. It keeps the size of the particles smaller, and also allows them to remain stable and dispersed in solution with time.
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The third conclusion that can be drawn from these results is that the simple formulation method demonstrated by polyQPA-Pluronic® nanoparticles would be an effective means to produce stable micelle drug delivery systems from hydrophobic polymers (like polyQPA). Having a simple preparation process is valuable for time and accuracy in the lab, and shows promising results for size, stability, and drug release ability.
In summary, the results of this research show promise for the future of
chemotherapy and specifically paclitaxel drug delivery systems. Although the size of the particles still remains too large for immediate drug delivery and all of these experiments were performed in vitro away from the actual conditions present in an actual tumor cell, the results of the research provide a promising start for future research.
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LIST OF REFERENCES
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Bae, Jungeun, Abhijeet Maurya, Zia Shariat-Madar, S. Narasimha Murthy, and
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